Electrode layer and battery

Abstract

A main object of the present disclosure is to provide an electrode layer having a low initial resistance.SOLUTION: The present disclosure solves the above problem by providing an electrode layer comprising an electrode active material comprising a Si element, and a solid electrolyte comprising an A element as a main component of an anion, wherein when an overlapping degree D of the Si element and the A element is calculated based on an element mapping image obtained by SEM-EDX measurement, the D is more than - 0.472 and 0 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electrode layer and a battery. [Background technology]

[0002] In recent years, the development of batteries has been actively pursued. For example, in the automotive industry, development of batteries for use in electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), or hybrid electric vehicles (HEVs) is underway. In addition, Si (silicon) is known as an electrode active material used in batteries. For example, Patent Document 1 discloses an active material containing Si, which has voids inside the primary particles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-167083 Summary of the Invention [Problem to be solved by the invention]

[0004] Electrode active materials containing Si element have a large theoretical capacity and are effective in increasing the energy density of batteries. On the other hand, it is expected that the higher the dispersion state of the electrode active material and solid electrolyte in the electrode layer, the lower the initial resistance will be. However, it was unexpectedly found that the initial resistance increases when the dispersion state of the electrode active material and solid electrolyte is too high.

[0005] The present disclosure has been made in view of the above circumstances, and has as its main object to provide an electrode layer having low initial resistance. [Means for solving the problem]

[0006] [1] An electrode layer containing an electrode active material containing Si element and a solid electrolyte containing A element as a main component of an anion, An electrode layer, wherein when an overlap degree D of the Si element and the A element is calculated based on an element mapping image obtained by SEM-EDX measurement, the D is greater than −0.472 and equal to or less than 0.

[0007] [2] The electrode layer according to [1], wherein the D is −0.39 or more.

[0008] [3] The electrode layer according to [1] or [2], wherein D is not less than −0.35 and not more than −0.10.

[0009] [4] The oxygen content of the electrode active material is 1.0% by mass or more and 10% by mass or less, The electrode layer contains a solvent component, The solvent component has a δp of 2.0 MPa in the Hansen solubility parameter (HSP). 0.5 The electrode layer according to any one of [1] to [3] below.

[0010] [5] The oxygen content of the electrode active material is 1.0% by mass or more and 10% by mass or less, The solid electrolyte has a δp of 10.0 MPa in the Hansen solubility parameter (HSP). 0.5 Above 15.0MPa 0.5 The electrode layer according to any one of [1] to [4] below.

[0011] [6] The electrode layer according to any one of [1] to [5], wherein the solid electrolyte is a sulfide solid electrolyte containing sulfur element as the A element.

[0012] [7] The electrode layer according to any one of [1] to [6], wherein the electrode active material is porous.

[0013] [8] The electrode layer according to any one of [1] to [7], wherein the electrode active material has a silicon clathrate crystal phase.

[0014] [9] The electrode layer according to any one of [1] to [8], wherein the electrode active material is a negative electrode active material.

[0015]

[10] A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, The battery, wherein the positive electrode layer or the negative electrode layer is the electrode layer according to any one of [1] to [9].

[0016]

[11] The battery according to

[10] , wherein the electrolyte layer contains a solid electrolyte. [Effects of the Invention]

[0017] The present disclosure has an effect of being able to obtain an electrode layer with low initial resistance. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. [Figure 2] This is a mapping image of Si. [Figure 3] This is a mapping image of S. [Figure 4] 10 is an image illustrating the degree of overlap D between Si and S. DETAILED DESCRIPTION OF THE INVENTION

[0019] The electrode layer and the battery according to the present disclosure will be described in detail below.

[0020] A. Electrode layer The electrode layer in the present disclosure contains an electrode active material containing Si element and a solid electrolyte containing A element as a main anion component. When the degree of overlap D between Si element and A element is calculated based on an element mapping image acquired by SEM-EDX measurement, the degree of overlap D is within a predetermined range.

[0021] According to the present disclosure, the degree of overlap D is within a predetermined range, resulting in an electrode layer with low initial resistance. As described above, Si has a large theoretical capacity and is effective in increasing the energy density of a battery. On the other hand, it is expected that the higher the dispersion state of the electrode active material and solid electrolyte in the electrode layer, the lower the initial resistance. However, it has been surprisingly found that if the dispersion state of the electrode active material and solid electrolyte is too high, the initial resistance becomes high. In contrast, in the present disclosure, the initial resistance of the electrode layer can be reduced by appropriately adjusting the dispersion state of the electrode active material and solid electrolyte.

[0022] In the present disclosure, SEM-EDX measurement is performed on a cross section of the electrode layer to obtain an element mapping image, and the overlap degree D of the Si element and the A element is calculated based on the obtained element mapping image. The overlap degree D is an index based on the so-called correlation coefficient. Details of the method for calculating the overlap degree D are described in the Examples below. The overlap degree D is typically greater than -0.472, and may be -0.42 or greater, -0.39 or greater, or even -0.35 or greater. If the overlap degree D is too low, the dispersion state of the electrode active material and the solid electrolyte is improved, but unexpectedly, the initial resistance is also increased. The reason for this is unclear, but it is presumed that the improved dispersion state of the electrode active material and the solid electrolyte results in insufficient electron conduction paths. On the other hand, the overlap degree D is typically 0 or less, and may be -0.05 or less, or -0.10 or less. If the degree of overlap D is too high, the dispersion state of the electrode active material and the solid electrolyte will be low, which may result in insufficient ion conduction paths and high initial resistance.

[0023] 1. Electrode active material The electrode active material in the present disclosure contains elemental Si. Examples of electrode active materials include simple Si, Si alloys, Si oxides, and Si carbides. Si alloys are alloys containing Si as the main component. Examples of metals other than Si in Si alloys include Na, W, Mo, Cr, V, Nb, Fe, Ti, Zr, and Hf. The Si alloy may contain only one metal other than Si, or two or more metals other than Si. Examples of Si oxides include SiO. Examples of Si carbides include SiC.

[0024] The oxygen content of the electrode active material is not particularly limited, but is, for example, 1.0% by mass or more and 10% by mass or less. The oxygen content of the electrode active material may be 3.0% by mass or more, or 5.0% by mass or more. On the other hand, the oxygen content of the electrode active material may be 9.0% by mass or less, 8.0% by mass or less, or 7.0% by mass or less. The oxygen content of the electrode active material is typically the amount of oxygen present on the surface of the electrode active material, and is a value measured, for example, with an oxygen-nitrogen-hydrogen (ONH) analyzer. For example, when the electrode active material is washed with a hydrofluoric acid aqueous solution, hydrogen termination occurs on the surface of the electrode active material, and the oxygen content on the surface of the electrode active material decreases.

[0025] The electrode active material is usually in the form of particles. The electrode active material may be primary particles or secondary particles formed by aggregation of primary particles. The electrode active material is preferably porous (porous Si). That is, the electrode active material preferably has voids inside the primary particles. The proportion of voids in the primary particles (porosity) is, for example, 4% or more, and may be 10% or more. The porosity may be, for example, 40% or less, and may be 20% or less. The porosity can be determined, for example, by the following procedure. First, a cross section of an electrode layer containing the electrode active material is obtained by ion milling. The cross section is then observed with a scanning electron microscope (SEM) to obtain a photograph of the particles. From the obtained photograph, the silicon portion and the void portion are clearly distinguished using image analysis software and binarized. The areas of the silicon portion and the void portion are determined, and the porosity (%) is calculated using the following formula: Porosity (%) = 100 × (area of ​​void part) / ((area of ​​silicon part) + (area of ​​void part))

[0026] The electrode active material preferably has many pores with a pore diameter of 5 nm or less. The pore volume P1 of the pores with a pore diameter of 5 nm or less is, for example, 0.015 cc / g or more, or may be 0.020 cc / g or more, or may be 0.023 cc / g or more. On the other hand, the pore volume P1 is, for example, 0.05 cc / g or less, or may be 0.04 cc / g or less, or may be 0.035 cc / g or less. In the present disclosure, the pore volume refers to the cumulative pore volume, and can be determined, for example, by BET measurement, gas adsorption method, mercury porosimeter measurement, 3D-SEM, or 3D-TEM.

[0027] The electrode active material preferably has many pores with a pore diameter of 10 nm or less. The pore volume P2 of the pores with a pore diameter of 10 nm or less is, for example, 0.030 cc / g or more, or may be 0.035 cc / g or more, or may be 0.040 cc / g or more. On the other hand, the pore volume P2 is, for example, 0.08 cc / g or less, or may be 0.07 cc / g or less, or may be 0.06 cc / g or less. Furthermore, the ratio of the pore volume P1 to the pore volume P2 (P1 / P2) is, for example, 50% or more, or may be 55% or more, or may be 57% or more. On the other hand, P1 / P2 is, for example, 80% or less, or may be 70% or less, or may be 65% or less.

[0028] The electrode active material preferably has many pores with a pore diameter of 100 nm or less. The pore volume P3 of the pores with a pore diameter of 100 nm or less is, for example, 0.10 cc / g or more, or may be 0.20 cc / g or more, or may be 0.32 cc / g or more. On the other hand, the pore volume P3 is, for example, 0.50 cc / g or less, or may be 0.45 cc / g or less, or may be 0.38 cc / g or less. Furthermore, the ratio of the pore volume P1 to the pore volume P3 (P1 / P3) is, for example, 6.0% or more, or may be 6.5% or more, or may be 6.9% or more. On the other hand, P1 / P3 is, for example, 15% or less, or may be 12% or less, or may be 10% or less.

[0029] One example of a method for producing a porous electrode active material is to produce an alloy of Li and Si (Li-Si alloy) and then remove Li from the Li-Si alloy. The Li-Si alloy can be obtained, for example, by mixing Li and Si. The ratio of Li to Si (Li / Si) is, for example, 1.0 or more, or may be 2.0 or more, 3.0 or more, or even 4.0 or more. On the other hand, Li / Si is, for example, 8.0 or less. One example of a method for removing Li from a Li-Si alloy is to react the Li-Si alloy with a Li extractant. Examples of Li extractants include alcohols such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol; and acids such as acetic acid, formic acid, propionic acid, and oxalic acid.

[0030] Another example of a method for producing a porous electrode active material is a method in which an alloy of Mg and Si (Mg—Si alloy) is produced and then Mg is removed from the Mg—Si alloy. The Mg—Si alloy can be obtained, for example, by heating a mixture of Mg and Si. The ratio of Mg to Si (Mg / Si) is, for example, 1.0 or more, or may be 1.5 or more, or even 2.0 or more. On the other hand, Mg / Si is, for example, 6.0 or less. An example of a method for removing Mg from an Mg—Si alloy is a method in which the Mg in the Mg—Si alloy is converted to MgO by heating the Mg—Si alloy in an oxygen-containing inert gas atmosphere, and then the MgO is removed with an acid solution. An example of the acid solution is an aqueous solution containing hydrochloric acid (HCl) and hydrogen fluoride (HF).

[0031] The electrode active material may be crystalline or amorphous. When the electrode active material is crystalline, the electrode active material usually has a Si crystalline phase. An example of the Si crystalline phase is a diamond-type crystalline phase. General Si contains the diamond-type crystalline phase as the Si crystalline phase. The electrode active material may contain the diamond-type crystalline phase as the main phase of the Si crystalline phase.

[0032] Another example of a Si crystalline phase is a silicon clathrate crystalline phase. The silicon clathrate crystalline phase may be a silicon clathrate I crystalline phase or a silicon clathrate II crystalline phase. In a silicon clathrate crystalline phase, multiple Si elements form a polyhedron (cage) including a pentagon or hexagon. This polyhedron has a space inside that can encapsulate metal ions such as Li ions. By inserting metal ions into this space, volume change due to charge and discharge can be suppressed. The electrode active material may contain a silicon clathrate I crystalline phase or a silicon clathrate II crystalline phase as the main phase of the Si crystalline phase. A method for producing a silicon clathrate crystalline phase includes, for example, reacting Na with Si to produce a Na-Si alloy, and then calcining the Na-Si alloy to remove Na from the Na-Si alloy.

[0033] Average particle size of the electrode active material (D 50 The average particle size (D) is not particularly limited, but may be, for example, 0.1 μm or more and 50 μm or less, or 0.5 μm or more and 30 μm or less. 50 ) can be calculated, for example, from measurements using a scanning electron microscope (SEM). The BET specific surface area of ​​the electrode active material is not particularly limited, but is, for example, 30 m 2 / g or more, and 40m 2 / g or more, and 2 / g or more, and 2 On the other hand, the BET specific surface area of ​​the electrode active material may be, for example, 150 m 2 / g or less.

[0034] The electrode active material may or may not be coated with a coating layer containing a solid electrolyte. The solid electrolyte constituting the coating layer is not particularly limited, but examples include the solid electrolytes described in "2. Solid Electrolytes" below, and among these, sulfide solid electrolytes are preferred. The coverage of the coating layer with respect to the electrode active material is, for example, 50% or more, or may be 70% or more, or may be 90% or more. The thickness of the coating layer is, for example, 1 nm or more and 100 nm or less, or may be 5 nm or more and 50 nm or less, or may be 10 nm or more and 30 nm or less.

[0035] The proportion of the electrode active material in the electrode layer is, for example, 20% by mass or more, or may be 30% by mass or more, or may be 40% by mass or more. If the proportion of the electrode active material is too low, sufficient energy density may not be obtained. On the other hand, the proportion of the electrode active material in the electrode layer is, for example, 80% by mass or less, or may be 70% by mass or less, or may be 60% by mass or less. If the proportion of the electrode active material is too high, the ionic conductivity and electronic conductivity of the electrode layer may relatively decrease.

[0036] 2.Solid electrolyte The electrode layer contains a solid electrolyte containing an element A as the main anion component. The addition of the solid electrolyte improves the ionic conductivity of the electrode layer. Examples of the solid electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes, halide solid electrolytes, and oxide solid electrolytes. Among these, the solid electrolyte is preferably a sulfide solid electrolyte because of its high ionic conductivity. A sulfide solid electrolyte is an electrolyte containing an element S as the element A, a halide solid electrolyte is an electrolyte containing an element X as the element A (X is, for example, at least one of F, Cl, Br, and I), and an oxide solid electrolyte is an electrolyte containing an element O as the element A.

[0037] The sulfide solid electrolyte typically contains at least Li and S. Preferably, the sulfide solid electrolyte further contains Me (Me is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In). The sulfide solid electrolyte may also contain a halogen element such as F, Cl, Br, or I.

[0038] The sulfide solid electrolyte may be a glass-based (amorphous) sulfide solid electrolyte, a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. The sulfide solid electrolyte may have a crystalline phase. Examples of the crystalline phase include a Thio-LISICON-type crystalline phase, an Argyrodite-type crystalline phase, and an LGPS-type crystalline phase.

[0039] The composition of the sulfide solid electrolyte is not particularly limited, but examples thereof include xLi2S·(1-x)P2S5 (0.5≦x<1), yLiI·zLiBr·(100-yz)(xLi2S·(1-x)P2S5) (0.5≦x<1, 0≦y≦30, 0≦z≦30). In these compositions, x preferably satisfies 0.7≦x≦0.8. Another example of the composition of the sulfide solid electrolyte is Li 7-x PS 6-x X x X is at least one of F, Cl, Br, and I, and x satisfies 0≦x<2. Another example of the composition of the sulfide solid electrolyte is Li4-x Me 1-x P x S4(0 < x < 1) can be cited. Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0040] The δp (polar term) in the Hansen solubility parameter (HSP) of the solid electrolyte is, for example, 10.0 MPa 0.5 or more, and may be 12.0 MPa 0.5 or more, and may be 12.5 MPa 0.5 or more. Also, the δp of the solid electrolyte is, for example, 15.0 MPa 0.5 or less. The δp (polar term) of the Hansen solubility parameter can be determined based on Hansen Solubility Parameters: A user's handbook, Second Edition. Boca Raton, Fla: CRC Press. (Hansen, Charles (2007)).

[0041] The proportion of the solid electrolyte in the electrode layer is, for example, 10% by mass or more, and may be 20% by mass or more, and may be 30% by mass or more. If the proportion of the solid electrolyte is too small, there may be insufficient ion conduction paths in the electrode layer. On the other hand, the proportion of the solid electrolyte in the electrode layer is, for example, 60% by mass or less, and may be 50% by mass or less. If the proportion of the solid electrolyte is too large, relatively, the proportion of the electrode active material will be small, and the energy density may be low.

[0042] 3. Binder The electrode layer may contain a conductive material. The binder may or may not contain an unsaturated bond. The unsaturated bond is preferably an olefinic unsaturated bond. The binder may have an unsaturated bond in its main chain or in its side chain. Examples of binders containing unsaturated bonds include butadiene rubber-based binders (BR-based binders) such as styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and butadiene rubber (BR); styrene-based block copolymers such as styrene-butadiene-styrene block copolymer (SBS) and styrene-isoprene-styrene block copolymer (SIS); and ethylene-propylene-diene copolymer (EPDM).

[0043] The proportion of the binder in the electrode layer is, for example, 0.5% by mass or more, and may be 1.0% by mass or more, or even 1.5% by mass or more. If the proportion of the binder is too low, it may be impossible to sufficiently reduce the increase in resistance due to charging and discharging. On the other hand, the proportion of the binder in the electrode layer is, for example, 5% by mass or less, and may be 3% by mass or less. If the proportion of the binder is too high, the proportion of the electrode active material will be relatively low, and this may result in a low energy density.

[0044] 4.Conductive materials The electrode layer may contain a conductive material. Addition of the conductive material improves the electronic conductivity of the electrode layer. Examples of the conductive material include carbon materials, metal particles, and conductive polymers. Examples of the carbon material include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF).

[0045] The proportion of the conductive material in the electrode layer is, for example, 0.1% by mass or more, or may be 0.5% by mass or more, or may be 1.0% by mass or more. If the proportion of the conductive material is too low, the electron conduction path in the electrode layer may be insufficient. On the other hand, the proportion of the conductive material in the electrode layer is, for example, 5% by mass or less, or may be 3% by mass or less. If the proportion of the conductive material is too high, the proportion of the electrode active material may be relatively low, and the energy density may be low.

[0046] 5. Electrode layer The electrode layer may contain a solvent component. The solvent component is, for example, a residual component of the solvent (dispersion medium) used when producing the electrode layer. The solvent component preferably has low polarity. If the polarity of the solvent component is high, for example, the dispersibility of the solid electrolyte is improved, but if the solvent component remains in the electrode layer, the remaining solvent component may cause deterioration of the solid electrolyte. On the other hand, if the polarity of the solvent component is low, deterioration of the solid electrolyte due to the remaining solvent component can be suppressed.

[0047] The solvent component has a δp in the Hansen solubility parameter (HSP) of, for example, 6.0 MPa. 0.5 less than 5.5MPa 0.5 It may be less than 4.0 MPa 0.5 It may be less than 3.5 MPa 0.5 It may be less than 2.0 MPa 0.5 It may be less than 1.5 MPa 0.5 It may be 1.0 MPa or less. 0.5 On the other hand, the Δp of the solvent component may be 0 MPa or less. 0.5 may be 0 MPa 0.5 Examples of the solvent component include tetralin, diisobutyl ketone, dodecane, isodecane, butyl butyrate, mesitylene, heptane, dibutyl ether, decane, and toluene.

[0048] The proportion of the solvent component in the electrode layer is, for example, 10 ppm or more, or may be 50 ppm or more, or may be 100 ppm or more. If the proportion of the solvent component is too low, the load of the step of drying the electrode layer may be large. On the other hand, the proportion of the solvent component in the electrode layer is, for example, 15,000 ppm or less, or may be 5,000 ppm or less, or may be 500 ppm or less. If the proportion of the solvent component is too high, the formability of the electrode layer may be reduced. The proportion of the solvent component in the electrode layer can be measured, for example, by gas chromatography mass spectrometry (GC-MS) or liquid chromatography mass spectrometry (LC-MS).

[0049] As described above, the electrode layer contains at least an electrode active material and a solid electrolyte containing element A as the main anion component. In the present disclosure, an organic compound having two or more benzene rings may be present between the electrode active material and the solid electrolyte. The organic compound has high chemical stability, and therefore can suppress deterioration of the solid electrolyte (e.g., reductive decomposition, oxidative decomposition) associated with charge and discharge. Therefore, an increase in resistance due to charge and discharge can be suppressed. In particular, it is preferable that the conjugation within one benzene ring extends to the outside of that benzene ring (e.g., the other benzene ring). Furthermore, the organic compound may be dispersed in the binder present between the electrode active material and the solid electrolyte.

[0050] Examples of organic compounds having two or more benzene rings include compounds represented by the following general formula (1) or (2).

[0051] [ka] (In the formula, R 1 and R 2 are each independently an organic group, and R 3 ~R 10 are each independently a hydrogen atom or a substituent, and n 1 is an integer between 0 and 4.)

[0052] An example of the compound represented by general formula (1) is 9,9-Bis(4-glycidyloxyphenyl)fluorene, which is represented by the following chemical formula (1).

[0053] [ka]

[0054] Other examples of organic compounds having two or more benzene rings include compounds represented by the following general formula (3).

[0055] [ka] (wherein S is a single bond or an organic group, and R 11 ~R 20 are each independently a hydrogen atom or a substituent.

[0056] An example of the compound represented by general formula (3) is 1,3-Diphenyl-2,3-epoxy-1-propanone, which is represented by the following chemical formula (2).

[0057] [ka]

[0058] The electrode layer in the present disclosure is typically used in batteries. The electrode layer may be either a negative electrode layer or a positive electrode layer, with the former being preferred. The thickness of the electrode layer is, for example, 0.1 μm or more and 1000 μm or less, or 0.1 μm or more and 500 μm or less, or 0.1 μm or more and 100 μm or less.

[0059] The method for producing the electrode layer is not particularly limited, and examples thereof include a production method having the following steps: a preparation step of preparing the electrode active material, a mixing step of mixing the electrode active material, the binder, and a solvent to obtain an electrode slurry, and an electrode layer formation step of forming an electrode layer using the electrode slurry. The present disclosure can also provide such a production method for the electrode layer.

[0060] The preparing step is a step of preparing the electrode active material. The electrode active material is the same as that described above in "1. Electrode Active Material." The mixing step is a step of mixing the electrode active material, the binder, and a solvent to obtain an electrode slurry. The solvent (dispersion medium) is the same as that described above. In the present disclosure, an electrode slurry containing the electrode active material, the binder, and the solvent can also be provided.

[0061] The electrode layer forming step is a step of forming an electrode layer using the electrode slurry. The method for forming the electrode layer is not particularly limited, and known methods can be used. For example, the method for forming the electrode layer includes a method in which the electrode slurry is applied to an electrode current collector and then dried. When forming the electrode layer, a pressing process may be performed to press the electrode layer in the thickness direction. Examples of the pressing process include a roller press and a flat plate press.

[0062] B.Battery Fig. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. The battery 10 shown in Fig. 1 includes a positive electrode layer 1, a negative electrode layer 2, an electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 that collects current from the positive electrode layer 1, and a negative electrode current collector 5 that collects current from the negative electrode layer 2. In the present disclosure, the positive electrode layer 1 or the negative electrode layer 2 is the electrode layer described above in "A. Electrode Layer."

[0063] According to the present disclosure, by using the above-described electrode layer, a battery with low initial resistance is obtained. As described above, the electrode layer may be a negative electrode layer or a positive electrode layer, but the former is preferred. Below, details of the battery when the electrode layer is a negative electrode layer will be described.

[0064] 1. Negative electrode layer The negative electrode layer is a layer containing at least a negative electrode active material. The negative electrode layer is the same as that described above in "A. Electrode layer," and therefore will not be described here.

[0065] 2. Positive electrode layer The positive electrode layer is a layer containing at least a positive electrode active material, and may also contain at least one of an electrolyte, a conductive material, and a binder, as necessary.

[0066] Examples of the positive electrode active material include oxide active materials, such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 and spinel-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0067] A coating layer containing a Li-ion conductive oxide may be formed on the surface of the oxide active material. This is because it can suppress the reaction between the oxide active material and the solid electrolyte (especially a sulfide solid electrolyte). An example of the Li-ion conductive oxide is LiNbO3. The thickness of the coating layer is, for example, 1 nm or more and 30 nm or less. Furthermore, Li2S, for example, can also be used as the positive electrode active material.

[0068] The positive electrode active material may be in the form of particles, for example. 50) is not particularly limited, but may be, for example, 10 nm or more, or may be 100 nm or more. On the other hand, the average particle diameter (D 50 ) is, for example, 50 μm or less, and may be 20 μm or less.

[0069] The electrolyte used in the positive electrode layer is the same as that described in "3. Electrolyte Layer." The conductive material and binder used in the positive electrode layer are the same as those described in "A. Electrode Layer" above, and therefore will not be described here. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less, or may be 0.1 μm or more and 500 μm or less, or may be 0.1 μm or more and 100 μm or less.

[0070] 3. Electrolyte layer The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and contains at least an electrolyte. The electrolyte may be a solid electrolyte or a liquid electrolyte (electrolytic solution).

[0071] The solid electrolyte is the same as that described above in "A. Electrode Layer," and therefore will not be described here. The electrolyte preferably contains a supporting salt and a solvent. Examples of supporting salts (lithium salts) for the lithium-ion conductive electrolyte include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3. Examples of solvents used in the electrolyte include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and chain esters (chain carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The electrolyte preferably contains two or more solvents.

[0072] The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less, or may be 0.1 μm or more and 500 μm or less, or may be 0.1 μm or more and 100 μm or less.

[0073] 4. Other configurations The battery according to the present disclosure preferably includes a positive electrode current collector that collects current from the positive electrode layer and a negative electrode current collector that collects current from the negative electrode layer. Examples of materials for the positive electrode current collector include stainless steel, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of materials for the negative electrode current collector include stainless steel, copper, nickel, and carbon.

[0074] The battery of the present disclosure may further include a restraining jig that applies a restraining pressure to the positive electrode layer, the electrolyte layer, and the negative electrode layer in the thickness direction. In particular, when the electrolyte layer is a solid electrolyte layer, it is preferable to apply a restraining pressure to form good ion conduction paths and electron conduction paths. The restraining pressure is, for example, 0.1 MPa or more, or may be 1 MPa or more, or may be 5 MPa or more. Meanwhile, the restraining pressure is, for example, 100 MPa or less, or may be 50 MPa or less, or may be 20 MPa or less.

[0075] 5.Battery The type of battery in the present disclosure is not particularly limited, but is typically a lithium-ion battery. Furthermore, the battery in the present disclosure may be a liquid battery whose electrolyte layer contains an electrolytic solution, or a solid battery whose electrolyte layer contains a solid electrolyte. The solid battery may be a semi-solid battery or an all-solid-state battery. In the present disclosure, a semi-solid battery is a battery whose electrolyte layer contains an inorganic solid electrolyte and a liquid component (e.g., an ionic liquid). In the present disclosure, an all-solid-state battery is a battery whose electrolyte layer contains only an inorganic solid electrolyte. Furthermore, the battery in the present disclosure may be a primary battery or a secondary battery, with secondary batteries being preferred. This is because they can be repeatedly charged and discharged, making them useful, for example, as automotive batteries.

[0076] Examples of uses of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, it is preferable to use the battery as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery may also be used as a power source for mobile objects other than vehicles (for example, trains, ships, and aircraft), and may also be used as a power source for electrical appliances such as information processing devices.

[0077] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0078] [Example 1] (Preparation of electrode active material) Metallic Li and Si powder were weighed out in a molar ratio of 4:1 and mixed in a mortar under an Ar atmosphere at room temperature for 0.5 hours to react. This produced Li4Si. The resulting Li4Si was then reacted with ethanol under an Ar atmosphere. The resulting reaction product is believed to contain Si and CH3CHOLi. The reaction product was filtered, and the filtered solid was dried at 120°C for at least 3 hours to produce powdered porous Si.

[0079] The obtained porous Si was used to produce a Na-Si alloy using NaH as a Na source. The NaH used was previously washed with hexane. NaH and porous Si were weighed out to a molar ratio of 1.05:1 and mixed using a cutter mill. The mixture of NaH and porous Si was heated in a heating furnace under an Ar atmosphere at 475°C for 40 hours to obtain a powdered Na-Si alloy.

[0080] Using the obtained Na-Si alloy and AlF3 as a Na trapping agent, silicon clathrate was produced by solid-phase method. The Na-Si alloy and AlF3 were weighed out to a molar ratio of 1:0.35 and mixed using a cutter mill to obtain a reaction material. The obtained powdered reaction material was placed in a stainless steel reaction vessel and heated in a heating furnace under an Ar atmosphere at 310°C for 60 hours to react, obtaining a precursor active material.

[0081] The obtained precursor active material is thought to contain NaF and Al as by-products. Therefore, the precursor active material was washed with a mixed solvent of HNO3 and HO in a volume ratio of 10:90. This removed the by-products from the reaction product. After washing, the mixture was filtered, and the filtered solid was dried at 120°C for at least 3 hours to obtain the electrode active material.

[0082] (Preparation of negative electrode) The resulting electrode active material, sulfide solid electrolyte (LiS-P2S5-based glass ceramic), conductive material (VGCF), and tetralin solution containing 5% by weight of binder (BR-based binder) were added to a polypropylene container and stirred for 30 seconds using an ultrasonic disperser (UH-50, manufactured by SMT). The container was then shaken for 30 minutes using a shaker (TTM-1, manufactured by Shibata Scientific Co., Ltd.) to obtain a negative electrode slurry. The mass ratio of the electrode active material, sulfide solid electrolyte, conductive material, and binder was 51.27:42.7:0.77:2.89 (electrode active material:sulfide solid electrolyte:conductive material:binder). The resulting negative electrode slurry was applied to a negative electrode current collector (Cu foil, manufactured by UACJ) using an applicator by the blade method and dried on a hot plate at 100 °C for 30 minutes. As a result, a negative electrode having a negative electrode current collector and a negative electrode layer was obtained.

[0083] (Preparation of positive electrode) The positive electrode active material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3A butyl butyrate solution containing 5% by mass of 02 (average particle size 6 μm), a sulfide solid electrolyte (Li2S-P2S5-based glass ceramic), a conductive material (VGCF), and a PVDF-based binder was added, and the mixture was stirred for 30 seconds using an ultrasonic disperser (UH-50, manufactured by SMT). The container was then shaken for 3 minutes using a shaker (TTM-1, manufactured by Shibata Scientific Co., Ltd.), followed by another 30 seconds of stirring using the ultrasonic disperser and another 3 minutes of shaking using the shaker to obtain a positive electrode slurry. The resulting positive electrode slurry was applied to a positive electrode current collector (Al foil, manufactured by Showa Denko KK) using an applicator by the blade method and dried for 30 minutes on a hot plate at 100 °C. This resulted in a positive electrode comprising a positive electrode current collector and a positive electrode layer. The area of ​​the positive electrode was smaller than that of the negative electrode.

[0084] (Fabrication of solid electrolyte layer) A sulfide solid electrolyte (Li2S-P2S5-based glass ceramic), a heptane solution containing 5% by mass of a BR-based binder, and heptane were added to a polypropylene container and stirred for 30 seconds using an ultrasonic disperser (UH-50, manufactured by SMT). The container was then shaken for 30 minutes using a shaker (TTM-1, manufactured by Shibata Scientific Co., Ltd.) to obtain a slurry. The resulting slurry was applied to a release sheet (Al foil) using an applicator by the blade method and dried on a hot plate at 100°C for 30 minutes. This resulted in a transfer member having a release sheet and a solid electrolyte layer.

[0085] (Fabrication of all-solid-state batteries) A bonding solid electrolyte layer was placed on the positive electrode layer of the positive electrode, set in a roll press, and pressed at 100 kN / cm and 165°C. This resulted in a first laminate. Next, the negative electrode was set in the roll press and pressed at 60 kN / cm and 25°C. This resulted in a pressed negative electrode. Then, a bonding solid electrolyte layer and a transfer member were placed in order from the negative electrode layer side. At this time, the bonding solid electrolyte layer and the solid electrolyte layer on the transfer member were placed facing each other. The resulting laminate was set in a flat uniaxial press and temporarily pressed at 100 MPa and 25°C for 10 seconds. Then, the release sheet was peeled off from the solid electrolyte layer. This resulted in a second laminate. Next, the bonding solid electrolyte layer of the first laminate and the solid electrolyte layer of the second laminate were placed facing each other, set in a flat uniaxial press, and pressed at 200 MPa and 120°C for 1 minute. This resulted in an all-solid-state battery.

[0086] [Example 2] An electrode active material (negative electrode active material) was obtained in the same manner as in Example 1, except that the resultant was dried at 120° C. for 3 hours or more, then subjected to liquid treatment with an aqueous HF solution for 1 hour, filtered, and the filtered solid content was dried at 120° C. for 3 hours or more. An all-solid-state battery was obtained in the same manner as in Example 1, except that the obtained electrode active material (negative electrode active material) was used when preparing a negative electrode slurry.

[0087] [Example 3] An electrode active material (negative electrode active material) was obtained in the same manner as in Example 1, except that the mixture was dried at 120° C. for 3 hours or more, then subjected to a liquid treatment with an HF aqueous solution for 1 hour, filtered, and the filtered solid content was dried at 120° C. for 3 hours or more. An all-solid-state battery was obtained in the same manner as in Example 1, except that the obtained electrode active material (negative electrode active material) was used when preparing a negative electrode slurry, and the amount of binder used was changed to 0.86 times.

[0088] [Comparative Example 1] A sulfide solid electrolyte (LiS-P2S5-based glass ceramic) was immersed in a tetralin solution containing 5% by mass of a binder (BR-based binder) for 1 hour and then dried to obtain a sulfide solid electrolyte having a coating layer on its surface. An all-solid-state battery was obtained in the same manner as in Example 1, except that the obtained sulfide solid electrolyte was used in the preparation of a negative electrode slurry and the amount of binder used was increased by 1.14 times.

[0089] [evaluation] (SEM observation) The electrode active materials obtained in Examples 1 and 2 were observed using a scanning electron microscope (SEM), and as a result, it was confirmed that the electrode active materials were porous and had voids inside the primary particles.

[0090] (XRD measurement) X-ray diffraction (XRD) measurements using CuKα radiation were performed on the electrode active materials obtained in Examples 1 and 2. As a result, it was confirmed that the electrode active materials had a silicon clathrate II type crystalline phase as the main phase.

[0091] (Overlap with Si and S elements) The cross section of the negative electrode layer in the all-solid-state batteries obtained in Examples 1 to 3 and Comparative Example 1 was processed, and SEM-EDX measurement was performed on the cross section of the negative electrode layer to obtain mapping images of Si and S. The measurement conditions were an EDX magnification of 1000x, an acceleration voltage of 5 kV, and a measurement time of 60 seconds. The mapping images were taken in an area of ​​50 μm × 50 μm or more.

[0092] The obtained mapping image was digitized using OpenCV and noise was removed using a Gaussian filter. Figure 2 shows the mapping image of Si; noise was removed from this mapping image, and then a binarized image was obtained. Figure 3 shows the mapping image of S; noise was removed from this mapping image, and then a binarized image was obtained. Next, the binarized image of Si and the binarized image of S were overlaid to obtain a composite image for evaluating the degree of overlap of Si and S.

[0093] The degree of overlap D was then calculated using the resulting composite image. Specifically, the correlation coefficient between Si and S was calculated for each pixel (1280 × 960), and the correlation coefficient (degree of overlap D) for the entire image was determined. The correlation coefficient was calculated using known image processing software. For reference, as shown in Figures 4(a) to 4(c), Si is represented by a mesh pattern and S is represented by a dot pattern. As shown in Figure 4(a), if Si and S completely match, the correlation coefficient is 1. Note that, as shown on the right side of Figure 4(a), areas where neither Si nor S exist are not counted. On the other hand, as shown in Figure 4(b), if Si and S do not completely match, the correlation coefficient is -1. Furthermore, as shown in Figure 4(c), if Si and S match in half of the entire area and only Si or only S exists in the other half, the correlation coefficient is 0.

[0094] (Oxygen measurement) The oxygen content of the electrode active materials prepared in Examples 1 and 2 was determined using an oxygen / nitrogen / hydrogen (ONH) analyzer (EMGA-930, manufactured by Horiba, Ltd.). The results are shown in Table 1.

[0095] (Measurement of initial resistance) Charge and discharge tests were conducted on the all-solid-state batteries obtained in Examples 1 to 3 and Comparative Example 1. Specifically, CCCV charging was performed at 0.1 C to 4.55 V, and then discharged at 1 C to 3.0 V. Next, after charging to 3.9 V, the batteries were charged at 0.1 C to 3.7 V and discharged at 14.7 mA for 5 seconds, and the initial resistance was calculated from the voltage drop. The results are shown in Table 1. The initial resistance values ​​in Table 1 are relative values, with the result of Comparative Example 1 set to 100.

[0096] [Table 1]

[0097] As shown in Table 1, it was confirmed that Examples 1 to 3 had a larger overlapping degree D of the Si element and the S element and a lower initial resistance than Comparative Example 1. In particular, Example 2 had a significantly lower initial resistance than Examples 1 and 2. It was also confirmed that the higher the dispersion state of the electrode active material and the solid electrolyte, the smaller the overlapping degree D, but that if the dispersion state of the electrode active material and the solid electrolyte is too high, as in Comparative Example 1, the initial resistance increases. It was also suggested that the overlapping degree D can be controlled by the polarity (oxygen content) of the surface of the electrode active material (Si), the polarity of the solvent (dispersion medium) used in the slurry, the polarity of the solid electrolyte, and the amount of binder.

[0098] In the present disclosure, as in Example 1, the oxygen content of the electrode active material is around 9 mass % (7 mass % to 11 mass %), and the Δp of the solvent component is 0.2 MPa. 0.5 Near (0 MPa 0.5 ~1.0MPa 0.5 , especially, 0 MPa 0.5 ~0.5MPa 0.5 ) and the δp of the solid electrolyte is 13.5 MPa 0.5 Near (12.5MPa 0.5 ~15.0MPa 0.5 ) may be adopted.

[0099] Furthermore, in the present disclosure, as in Examples 2 and 3, the oxygen content of the electrode active material is around 5 mass % (3 mass % to 7 mass %), and Δp of the solvent component is 0.2 MPa. 0.5 Near (0 MPa 0.5 ~1.0MPa 0.5 , especially, 0 MPa 0.5 ~0.5MPa 0.5 ) and the δp of the solid electrolyte is 13.5 MPa 0.5 Near (12.5MPa 0.5 ~15.0MPa 0.5 ) may be adopted. [Explanation of symbols]

[0100] 1...Positive electrode layer 2...Anode layer 3...electrolyte layer 4 …Positive current collector 5 … Negative current collector 10 … batteries

Claims

1. An electrode layer comprising an electrode active material containing Si element and a solid electrolyte containing A element as a main component of an anion, An electrode layer, wherein when an overlapping degree D of the Si element and the A element is calculated based on an element mapping image acquired by SEM-EDX measurement, the D is greater than −0.472 and equal to or less than 0.

2. 2. The electrode layer according to claim 1, wherein D is −0.39 or more.

3. 2. The electrode layer according to claim 1, wherein D is −0.35 or more and −0.10 or less.

4. The oxygen content of the electrode active material is 1.0% by mass or more and 10% by mass or less, the electrode layer contains a solvent component, The solvent component has a δp of 2.0 MPa in the Hansen solubility parameter (HSP). ０．５ 2. The electrode layer of claim 1, wherein:

5. The oxygen content of the electrode active material is 1.0% by mass or more and 10% by mass or less, The solid electrolyte has a δp of 10.0 MPa in Hansen solubility parameter (HSP). ０．５ More than 15.0 MPa ０．５ 2. The electrode layer of claim 1, wherein:

6. The electrode layer according to claim 1 , wherein the solid electrolyte is a sulfide solid electrolyte containing sulfur as the A element.

7. The electrode layer of claim 1 , wherein the electrode active material is porous.

8. The electrode layer according to claim 1 , wherein the electrode active material has a silicon clathrate-type crystalline phase.

9. The electrode layer according to claim 1 , wherein the electrode active material is a negative electrode active material.

10. A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, A battery, wherein the positive electrode layer or the negative electrode layer is the electrode layer according to any one of claims 1 to 9.

11. 11. The battery of claim 10, wherein the electrolyte layer comprises a solid electrolyte.

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